An inclined plane makes an angle 30o with the horizontal. A groove (OA) of length 5 m cut in the plane makes an angle 30^o with OX. A short smooth cylinder is free to slide down under the influence of gravity. The time taken by the cylinder to reach from A to O is : g = 10 m/s²

2 s 

Acceleration of cylinder down the plane is : a

a = (g sin 30^o) (sin 30^o)

   = 10 \(\frac{1}{2} \frac{1}{2}\)

   = 2.5 m/s²

Time : t = \(\sqrt{\frac{2 S}{a}} = \sqrt{\frac{2*5}{2.5}}\)

t = 2 s